Tesla's parabolic rally has sent shares up 21% Tuesday, following a 19% surge Monday and putting gains at over 100% year-to-date.

While bulls are cheering the record run, short-sellers are also weighing in on what's next for the Elon Musk-led automaker.

In a tweet Tuesday, Citron Research, which is run by famed short-seller Andrew Left, said that the firm loves Tesla and promised to never be short the equity again.

Still, the message continued, "when the computers start driving the market, we believe even Elon would short the stock here if he was a fund manager. This is no longer about the technology, it has become the new Wall St casino."

But in October 2018, he made a surprising pivot by dropping his short position and going long on Tesla. His reasoning? "Plain and simple - Tesla is destroying the competition," he wrote in a blog post. He did not drop his lawsuit against Tesla and Musk when he went long on the stock.

The bullish bet didn't last long. In April 2019, he dropped his position, saying he had become frustrated with how the company was corresponding with shareholders. Still, even though Left shed his long Tesla bet, he said that he was not short the stock.